Dishwasher Install ?

I purchased a new DW and included with it was a DW Install kit. I opened the kit and when I went to attach the wires (blk/blk, wht/wht, grn/ground) I noticed the plug only had green, which is the center wire. The other wires dont have any center colors, but the insulation covering them are different. One is smooth and the other has ridges.

Could someone please let me know which wires I need to connect to the blk and wht, everything is done except this.